Display panel

Abstract

This application discloses a display panel, which includes a substrate, a first electrode, a light-emitting functional layer, and a second electrode. The first electrode is disposed on the substrate. The light-emitting functional layer is disposed on the side of the first electrode away from the substrate. The light-emitting functional layer includes a first light-emitting layer, a charge-generating layer, and a second light-emitting layer sequentially disposed on the first electrode. The first light-emitting layer includes a first light-emitting sublayer. The second light-emitting layer includes a second light-emitting sublayer. The second electrode is disposed on the side of the second light-emitting layer away from the charge-generating layer. The first light-emitting sublayer has a first thin-film compactness parameter, which is greater than or equal to a first threshold. The second light-emitting sublayer has a second thin-film compactness parameter, which is greater than or equal to a second threshold. The first and second thin-film compactness parameters are determined by the deformation of the thin film under unit force conditions.

Description

Technical Field

[0001] This application relates to the field of display technology, and more particularly to a display panel. Background Technology

[0002] Organic light-emitting diode (OLED) display panels have the characteristics of self-illumination, fast response, and wide viewing angle, and have a very broad application prospect.

[0003] In current commercial applications, single-layer OLED devices with a single light-emitting unit are approaching their performance limits. Therefore, scientists connect multiple light-emitting units through a charge generation layer to achieve higher luminous efficiency and longer device lifetime. The structure of a stacked OLED device connects the first and second light-emitting units through a charge generation layer. Due to the presence of the charge generation layer, a charge carrier injected by the electrode can flow sequentially through two independent light-emitting units, significantly improving luminous efficiency.

[0004] However, in the existing structural design strategies of OLED display panels, more consideration is given to the arrangement of molecular orbital energy levels in each functional layer. However, optimizing the energy level arrangement is more about optimizing the efficiency of OLED devices. However, efficiency is not the main reason that limits the large-scale commercial use of blue phosphorescent OLED devices. It is because the lifespan of existing blue phosphorescent OLED devices is generally short, which leads to the limited application of blue phosphorescent OLED light-emitting devices. Summary of the Invention

[0005] This application provides a display panel for improving the service life of the display panel.

[0006] This application provides a display panel, including:

[0007] Substrate,

[0008] A first electrode is disposed on the substrate;

[0009] A light-emitting functional layer is disposed on the side of the first electrode away from the substrate. The light-emitting functional layer includes a first light-emitting layer, a charge-generating layer and a second light-emitting layer sequentially disposed on the first electrode. The first light-emitting layer includes a first light-emitting sublayer and the second light-emitting layer includes a second light-emitting sublayer.

[0010] The second electrode is disposed on the side of the second light-emitting layer away from the charge-generating layer;

[0011] The first light-emitting sublayer has a first film compactness parameter, which is greater than or equal to a first threshold. The second light-emitting sublayer has a second film compactness parameter, which is greater than or equal to a second threshold. The first film compactness parameter and the second film compactness parameter are determined by the deformation of the film under unit force conditions.

[0012] Optionally, in some embodiments provided in this application, the first film compactness parameter and the second film compactness parameter are determined by the thickness deformation of the stressed portion of the film under unit force in the thickness direction of the film.

[0013] Optionally, in some embodiments provided in this application, the compactness parameter of the first thin film can be calculated by the following formula:

[0014] X1 = ΔF1 / ΔH1;

[0015] Where ΔF1 is the difference between different forces in the thickness direction of the film; ΔH1 is the thickness difference of the stressed part of the film under different forces.

[0016] The compactness parameter of the second thin film can be calculated using the following formula:

[0017] X2 = ΔF2 / ΔH2;

[0018] Wherein, ΔF2 is the difference between different forces in the thickness direction of the film; ΔH2 is the difference in thickness of the stressed part of the film under different forces.

[0019] Optionally, in some embodiments provided in this application, the first threshold is -1.7, and the first film compactness parameter is less than 0;

[0020] The second threshold is -1.7, and the second film compactness parameter is less than 0.

[0021] Optionally, in some embodiments provided in this application, when the display panel is powered on, the ratio between the dimensional deformation of the light-emitting functional layer and the original shape and size of the light-emitting functional layer is less than or equal to 7.5%.

[0022] Optionally, in some embodiments provided in this application, when the display panel is powered on, the ratio between the thickness expansion of the light-emitting functional layer and the original thickness of the light-emitting functional layer is less than or equal to 7.5%.

[0023] Optionally, in some embodiments provided in this application, when the display panel is heated, the ratio between the dimensional deformation of the light-emitting functional layer and the original shape and size of the light-emitting functional layer is less than or equal to 13%.

[0024] Optionally, in some embodiments provided in this application, when the display panel is heated, the ratio between the thickness expansion of the light-emitting functional layer and the original thickness of the light-emitting functional layer is less than or equal to 13%.

[0025] Optionally, in some embodiments provided in this application, the charge generation layer includes a first charge generation layer and a second charge generation layer. The first charge generation layer is disposed on the side of the first light-emitting layer away from the first electrode, and the first charge generation layer includes an n-type charge generation material. The second charge generation layer is disposed on the side of the first charge generation layer away from the first light-emitting layer, and the second charge generation layer includes a p-type charge generation material.

[0026] Optionally, in some embodiments provided in this application, the first light-emitting layer includes a first hole injection sublayer, a first hole transport sublayer, the first light-emitting sublayer, a first electron transport sublayer, and a first electron injection sublayer stacked sequentially.

[0027] The second light-emitting layer includes a second hole injection sublayer, a second hole transport sublayer, a second light-emitting sublayer, a second electron transport sublayer, and a second electron injection sublayer, which are stacked sequentially.

[0028] Optionally, in some embodiments provided in this application, the first light-emitting sublayer includes a blue phosphorescent material or a blue fluorescent material, and the second light-emitting sublayer includes a blue phosphorescent material or a blue fluorescent material.

[0029] This application provides a display panel, which includes a substrate, a first electrode, a light-emitting functional layer, and a second electrode. The first electrode is disposed on the substrate. The light-emitting functional layer is disposed on the side of the first electrode away from the substrate. The light-emitting functional layer includes a first light-emitting layer, a charge-generating layer, and a second light-emitting layer sequentially disposed on the first electrode. The first light-emitting layer includes a first light-emitting sublayer. The second light-emitting layer includes a second light-emitting sublayer. The second electrode is disposed on the side of the second light-emitting layer away from the charge-generating layer. The first light-emitting sublayer has a first thin-film compactness parameter, which is greater than or equal to a first threshold. The second light-emitting sublayer has a second thin-film compactness parameter, which is greater than or equal to a second threshold. The first and second thin-film compactness parameters are determined by the deformation of the thin film under unit force conditions.

[0030] The inventors of this application have discovered that when the first thin film density parameter of the first light-emitting sublayer is greater than or equal to a first threshold, and the second thin film density parameter of the second light-emitting sublayer is greater than or equal to a second threshold, the thin film density parameter and the lifespan of the display panel are positively correlated. The larger the thin film density parameter, the greater the thin film density, and the longer the lifespan of the display panel. Furthermore, since display panels with a stacked structure formed by multiple light-emitting units connected in series generate heat during operation, this heat causes the film thickness of the display panel to expand, leading to changes in the microcavity length. These changes in microcavity length cause a shift in the emitted color of the device, resulting in uneven display. The applicants of this application have discovered that when the first thin film density parameter of the first light-emitting sublayer is greater than or equal to the first threshold, and the second thin film density parameter of the second light-emitting sublayer is greater than or equal to the second threshold, the phenomenon of thermo-induced color shift caused by heat generation in display panels formed by multiple light-emitting units connected in series can be effectively improved. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the structure of a display panel provided in an embodiment of this application;

[0033] Figure 2 This is a schematic diagram illustrating the characterization of the thin film compactness parameters of the first luminescent layer using atomic force microscopy in this embodiment;

[0034] Figure 3 The linear relationship fitted to the first luminescent sublayer using mCP as the main material in the embodiments of this application;

[0035] Figure 4 The chemical structural formula of the organic light-emitting material provided in the embodiments of this application;

[0036] Figure 5 This is a diagram illustrating an energy level arrangement of a display panel provided in an embodiment of this application. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Please refer to the figures in the drawings, where the same component symbols represent the same components. The following description is based on the specific embodiments of this application shown, and should not be considered as limiting other specific embodiments not detailed herein. The term "embodiment" as used in this specification means example, illustration, or illustration.

[0038] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0039] This application provides a display panel. The following provides a detailed description of each. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments.

[0040] The display panel provided in this application will be described in detail below through specific embodiments.

[0041] Please refer to Figure 1 , Figure 1 This application provides a schematic diagram of a display panel structure. The display panel 100 includes a substrate 101, a first electrode 102, a light-emitting functional layer 10, and a second electrode 106. The first electrode 102 is disposed on the substrate 101. The light-emitting functional layer 10 is disposed on the side of the first electrode 102 away from the substrate 101. The light-emitting functional layer 10 includes a first light-emitting layer 103, a charge-generating layer 104, and a second light-emitting layer 105 sequentially disposed on the first electrode 102. The first light-emitting layer 103 includes a first light-emitting sublayer 1033. The second light-emitting layer 105 includes a second light-emitting sublayer 1053. The second electrode 106 is disposed on the side of the second light-emitting layer 105 away from the charge-generating layer 104. The first light-emitting sublayer 1033 has a first thin-film density parameter, which is greater than or equal to a first threshold. The second light-emitting sublayer 1053 has a second thin-film density parameter, which is greater than or equal to a second threshold. The first and second thin-film density parameters are determined by the deformation of the thin film under unit force conditions.

[0042] The inventors of this application have discovered that when the first thin film density parameter of the first light-emitting sublayer 1033 is greater than or equal to a first threshold, and the second thin film density parameter of the second light-emitting sublayer 1053 is greater than or equal to a second threshold, the thin film density parameter and the lifespan of the display panel 100 are positively correlated. The larger the thin film density parameter, the greater the thin film density, and the longer the lifespan of the display panel 100. Furthermore, since the display panel 100, with its stacked structure formed by multiple light-emitting units connected in series, generates heat during operation, this heat causes the film thickness of the display panel 100 to expand, resulting in a change in the microcavity length. This change in microcavity length leads to a shift in the emitted color of the device, resulting in uneven display. The applicants of this application have discovered that when the first thin film density parameter of the first light-emitting sublayer 1033 is greater than or equal to the first threshold, and the second thin film density parameter of the second light-emitting sublayer 1053 is greater than or equal to the second threshold, the phenomenon of thermo-induced color shift caused by heat generation in the display panel 100 formed by multiple light-emitting units connected in series can be effectively improved.

[0043] It should be understood that, in the embodiments of this application, the first film density parameter is related to the film density of the first light-emitting layer 1033; the higher the film density, the larger the first film density parameter. The second film density parameter is related to the film density of the second light-emitting layer 1053; the higher the film density, the larger the second film density parameter.

[0044] In this embodiment, when the first film density parameter of the first light-emitting sublayer 1033 is greater than or equal to a first threshold, the larger the first film density parameter, the greater the film density of the first light-emitting sublayer 1033. When the second film density parameter of the second light-emitting sublayer 1053 is greater than or equal to a second threshold, the larger the second film density parameter, the greater the film density of the second light-emitting sublayer 1053. This effectively improves the phenomenon of thermo-induced color shift caused by heat generation in the display panel 100 formed by multiple light-emitting units connected in series, thereby improving the uneven display of the display panel 100.

[0045] It should be noted that, in the embodiments of this application, the unit force includes, but is not limited to, the force applied to the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053. Here, the unit force refers to the smallest unit force applied to the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053 for measurement purposes, such as 1N, 2N, 5N, 10N, etc.

[0046] It should be noted that, in the embodiments of this application, the deformation generated by the thin film includes, but is not limited to, the deformation of the film thickness.

[0047] In some embodiments, the first and second film compactness parameters are determined by the thickness deformation of the stressed portion of the film under unit force in the thickness direction of the film. Specifically, the first film compactness parameter can be calculated by the following formula: X1 = ΔF1 / ΔH1, where X1 is the first film compactness parameter, ΔF1 is the difference between different forces in the thickness direction of the film, ΔH1 is the thickness difference of the stressed portion of the film under different forces, and 0 > X1 ≥ -1.7 N / cm.

[0048] In other words, the first threshold is -1.7 N / cm. When the first film density parameter is greater than or equal to -1.7 and less than 0, the larger the first film density parameter is, the higher the film density is, and the more uniform the display panel 100 is.

[0049] The second film compactness parameter can be calculated by the following formula: X2=ΔF2 / ΔH2, where X2 is the second film compactness parameter, ΔF2 is the difference between different forces in the thickness direction of the film, ΔH2 is the thickness difference of the stressed part of the film under different forces, and 0>X2≥-1.7N / cm.

[0050] In other words, the second threshold is -1.7 N / cm. When the second film density parameter is greater than or equal to -1.7 and less than 0, the larger the second film density parameter is, the higher the film density is, and the more uniform the display panel 100 is.

[0051] Wherein, ΔF1 or ΔF2 can be the difference between two different forces applied to the same stressed part, and ΔH1 or ΔH2 is the difference in thickness corresponding to the two different forces. Alternatively, ΔF1 or ΔF2 can be the difference in forces applied to two different stressed parts, and ΔH1 or ΔH2 is the difference in thickness corresponding to the two different forces.

[0052] It should be noted that in the embodiments of this application, the greater the unit force on the film, the smaller the thickness of the corresponding film.

[0053] In this application, atomic force microscopy (AFM) can be used to characterize the first thin film compactness parameters of the first luminescent sublayer 1033 and the second thin film compactness parameters of the second luminescent sublayer 1053. Under AFM characterization, the thickness of the first luminescent sublayer 1033 shows a linear relationship with the force exerted on it by the AFM probe; the slope of this linear relationship is the second thin film compactness parameter. Similarly, the thickness of the second luminescent sublayer 1053 shows a linear relationship with the force exerted on it by the AFM probe; the slope of this linear relationship is also the second thin film compactness parameter.

[0054] Specifically, the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053 are characterized using atomic force microscopy. Then, a linear relationship is established between the thickness of the first light-emitting sublayer 1033 and the force exerted on the first light-emitting sublayer 1033 by the probe of the atomic force microscope, and a linear relationship is also established between the thickness of the second light-emitting sublayer 1053 and the force exerted on the second light-emitting sublayer 1053 by the probe of the atomic force microscope. The greater the slope of the linear relationship, the greater the density of the thin film of the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053, which is more conducive to improving the thermal color shift phenomenon of the display panel 100.

[0055] Please refer to Figure 2 , Figure 2 This is a schematic diagram illustrating the characterization of the first film compactness parameters of the first luminescent sublayer using atomic force microscopy in this embodiment. The evaluation of the film compactness parameters of the first luminescent sublayer 1033 specifically includes the characterization of the first luminescent sublayer 1033 using atomic force microscopy.

[0056] The process of characterizing the first luminescent sublayer 1033 using atomic force microscopy may include depositing the first luminescent sublayer 1033 on a substrate S, and then using a probe P to detect the relative thickness of the first luminescent sublayer 1033. Depositing the first luminescent sublayer 1033 on the substrate S includes depositing a polyimide layer PI on the substrate S, with the polyimide layer PI covering a portion of the substrate S. Subsequently, the first luminescent sublayer 1033 is deposited on the substrate S by vapor deposition, covering the polyimide layer PI and the substrate S. The polyimide layer PI is then removed, thereby obtaining the first luminescent sublayer 1033 on the substrate S. In the embodiments of this application, the first luminescent sublayer 1033 only covers a portion of the substrate S, thereby creating a height difference for measuring the relative thickness of the first luminescent sublayer 1033. The steps for detecting the relative thickness of the first luminescent sublayer 1033 using probe P include: First, randomly selecting any point on the first luminescent sublayer 1033, applying a first force to it using probe P, and then applying the first force to the substrate S to measure the first relative thickness of the first luminescent sublayer 1033. Next, randomly selecting another point on the first luminescent sublayer 1033, applying a second force to it using probe P, and then applying the second force to the substrate S to measure the second relative thickness of the first luminescent sublayer 1033. This process is repeated, using a third force to measure the third relative thickness of the first luminescent sublayer 1033, and a fourth force to measure the fourth relative thickness of the luminescent layer. The Nth relative thickness of the first luminescent sublayer 1033 is then measured using the Nth force. Finally, the slope of the fitted linear relationship, with the force exerted on the first luminescent sublayer 1033 as the abscissa and the thickness of the first luminescent sublayer 1033 as the ordinate, is used as the first thin film compactness parameter of the first luminescent sublayer 1033. The greater the slope, the greater the film density of the first photonic layer 1033, which is more conducive to improving the thermal color shift phenomenon of the display panel 100.

[0057] In this embodiment, the thickness of the first light-emitting sublayer 1033 decreases as the force exerted by the probe P on the first light-emitting sublayer 1033 increases. The greater the force exerted by the probe P on the first light-emitting sublayer 1033, the smaller the corresponding thickness of the first light-emitting sublayer 1033. In this embodiment, the force exerted by the probe P on the first light-emitting sublayer 1033 is used as the abscissa, and the thickness of the first light-emitting sublayer 1033 is used as the ordinate to fit the corresponding linear relationship.

[0058] Please refer to Figure 3 , Figure 3The linear relationship fitted to the first luminescent sublayer using mCP (N,N-dicarbazo-3,5-benzene) as the host material for the first luminescent sublayer is provided in this embodiment of the application. In this embodiment, the force (F) exerted by the probe on the first luminescent sublayer 1033 is used as the abscissa, and the thickness (T) of the first luminescent sublayer 1033 is used as the ordinate. The slope of the fitted linear relationship is used as the first film compactness parameter of the first luminescent sublayer 1033, where the slope is -1.69.

[0059] It should be understood that the principle of characterizing the compactness parameters of the second thin film of the second luminescent sublayer 1053 using atomic force microscopy is the same as that of the first luminescent sublayer 1033, and will not be repeated here.

[0060] Specifically, in this application embodiment, 10 different organic light-emitting materials are used as the main materials of the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053 to evaluate the film density and luminescence performance of the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053. Please refer to... Figure 4 , Figure 4 The chemical structural formulas of the organic light-emitting materials provided in the embodiments of this application are shown below. The organic light-emitting materials include DCB, CBP, CDBP, CBPE, mCP, BCzph, CzC, 4CzPBP, TPBi, BCzTPM, BCPPA, NPB, TAPC, and Firmic.

[0061] Please refer to Table 1, which shows the performance test results of display panels using 10 different organic light-emitting materials as the main material.

[0062] Table 1:

[0063]

[0064]

[0065] As shown in Table 1, with the increase of film density, the voltage decreases slightly, the external quantum efficiency (EQE) increases slightly, and the lifetime improvement is very significant. This proves that higher film density is more beneficial to the performance of the multilayer blue phosphorescent device. In addition, the changes in CIEy (ΔCIEy), emission peak position (ΔP), and full width at half maximum (Fw) of the device at room temperature and 60 degrees Celsius were measured, and the results are shown in Table 1. The experimental results show that the higher the film density, the smaller the thermally induced color shift.

[0066] It should be noted that the slope is measured using atomic force microscopy applied to the thin films of the first luminescent layer 1033 and the second luminescent layer 1053. When the slope is greater than or equal to -1.7, the smaller the thermochromic shift, the more significant the improvement in the lifespan of the display panel 100. Of course, the first threshold can also be selected from -1.65, -1.6, -1.55, -1.5, -1.45, -1.4, -1.35, -1.3, -1.25, -1.2, -1.15, etc. The second threshold can also be selected from -1.65, -1.6, -1.55, -1.5, -1.45, -1.4, -1.35, -1.3, -1.25, -1.2, -1.15, etc.

[0067] Compared to red and green phosphorescent materials, blue phosphorescent materials have a particularly short lifespan, resulting in a decrease in the overall lifespan and reliability of the display panel 100. In this embodiment, taking blue phosphorescent material as an example, by increasing the film density of the blue phosphorescent material, the thermal color shift amplitude is reduced, thereby improving the lifespan and reliability of the display panel 100 made of blue phosphorescent material, and thus enhancing its market competitiveness.

[0068] In some embodiments, the first luminescent sublayer 1033 includes, but is not limited to, a blue phosphorescent material or a blue fluorescent material. The first luminescent sublayer 1033 may also be a red phosphorescent material, a green phosphorescent material, a red fluorescent material, or a green fluorescent material. The second luminescent sublayer 1053 includes, but is not limited to, a blue phosphorescent material or a blue fluorescent material. The second luminescent sublayer 1053 may also be a red phosphorescent material, a green phosphorescent material, a red fluorescent material, or a green fluorescent material.

[0069] In this embodiment, atomic force microscopy (AFM) is used to characterize the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053. A linear relationship is established between the thickness of the first light-emitting sublayer 1033 and the force exerted by the AFM probe on it, and a linear relationship is also established between the thickness of the second light-emitting sublayer 1053 and the force exerted by the AFM probe on it. The larger the slope of the linear relationship, the higher the film density parameter of the first and second light-emitting sublayers 1033 and 1053. A higher film density parameter results in a higher density of the first and second light-emitting sublayers 1033 and a smaller thermal displacement amplitude, leading to a longer lifespan for the display panel 100. In this embodiment, when the first film density parameter is greater than or equal to a first threshold, and the second film density parameter is greater than or equal to a second threshold, the lifespan of the display panel 100 is significantly improved.

[0070] In some embodiments of this application, the film formation quality of the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053 can also be evaluated by measuring the dimensional deformation of the display panel 100.

[0071] To further evaluate the film formation quality of the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053, when the display panel 100 is powered on, the ratio between the size change of the light-emitting functional layer 10 and the original shape and size of the light-emitting functional layer 10 is less than or equal to 7.5%.

[0072] It should be noted that the size variation of the light-emitting functional layer 10 includes, but is not limited to, the thickness expansion of the light-emitting functional layer 10.

[0073] In some embodiments, when the display panel 100 is powered on, the ratio between the thickness expansion of the light-emitting functional layer 10 and the original thickness of the light-emitting functional layer 10 is less than or equal to 7.5%.

[0074] For example, the light-emitting functional layer 10 has a first thickness 'a' before it is powered on. After the light-emitting functional layer 10 is lit up at a preset brightness for a preset working time, the light-emitting functional layer 10 has a second thickness 'b'. The thickness expansion ω1 of the second thickness 'b' and the first thickness 'a' is less than or equal to 7.5%, where ω1 = [(ba) / a] * 100%.

[0075] In some embodiments, the preset brightness can be 100 nits, and the preset time can be 1 hour. Specifically, after the light-emitting functional layer 10 operates at a brightness of 100 nits for 1 hour, the thickness before and after emitting light is measured using an interferometer.

[0076] In some embodiments, the thickness of the light-emitting functional layer 10 before and after heating can also be evaluated by heating the display panel 100.

[0077] In the case of the display panel 100 under heating state, the ratio between the deformation of the light-emitting functional layer 10 and the original shape and size of the light-emitting functional layer 10 is less than or equal to 13%.

[0078] In some embodiments, when the display panel 100 is heated, the ratio between the expansion of the thickness of the light-emitting functional layer 10 and the original thickness of the light-emitting functional layer 10 is less than or equal to 13%.

[0079] Specifically, the light-emitting functional layer 10 before heating has a first thickness a. After being heated at a preset temperature for a preset working time, the light-emitting functional layer 10 has a second thickness c. The thickness expansion ω2 between the second thickness c and the first thickness a is less than or equal to 13%. Wherein, ω2 = [(ca) / a] * 100%.

[0080] The preset temperature can be 100 degrees Celsius, and the preset working time can be 1 hour. Specifically, the light-emitting functional layer 10 is heated to 100 degrees Celsius and maintained at 100 degrees Celsius for 1 hour. The thickness of the heated light-emitting functional layer 10 is then measured using an interferometer.

[0081] Please refer to Table 2, which shows the thickness expansion of the light-emitting functional layer 10 of the display panel 100 under power-on and heating conditions.

[0082] Table 2:

[0083] Organic light-emitting materials ω1 ω2 DCB 10.1％ 15.1％ CBP 9.4％ 14.5％ CDBP 8.7％ 13.9％ CBPE 8.1％ 13.3％ mCP 7.6％ 12.7％ BCzPh 7.0％ 12.1％ CzC 6.7％ 11.4％ 4CzPBP 5.6％ 10.8％ BCzTPM 5.0％ 10.2％ BCPPA 4.7％ 9.6％

[0084] As shown in Table 2, by measuring the thickness of the display panel 100 before and after heating using an interferometer, the thickness expansion amplitude before and after heating is obtained. The smaller the thickness expansion amplitude, the better the film formation quality of the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053, the higher the film density of the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053, and the better the performance of the display panel 100. The smaller the thickness expansion amplitude after heating, the better the device. It should be noted that in practical applications, the maximum value of ω1 can be selected as 7.5%, 7%, 6.5%, 6%, 5.5%, 5%, 4.5%, etc.; the maximum value of ω2 can be selected as 13%, 12.5%, 12%, 11.5%, 11%, 10.5%, 10%, 9.5%, 9%, etc.

[0085] As can be seen from Tables 1 and 2, the higher the film density parameter of the first and second light-emitting layers, the higher the film density, the better the light-emitting performance of the device, the smaller the thickness expansion after heating, the smaller the thermal color shift, the more uniform the display, and the longer the lifespan of the display panel 100.

[0086] In this embodiment, the film quality of the light-emitting layer of the display panel 100 is evaluated from two dimensions. This includes evaluating the density of the first light-emitting sublayer 1033 and the second light-emitting sublayer 1053, and evaluating the thickness of the display panel 100 as a whole before and after heating. The evaluation of the film quality of the display panel 100 from these two dimensions shows that, under atomic force microscopy, a larger slope indicates a larger film density parameter of the light-emitting sublayer, and thus a higher light-emitting sublayer density. As the light-emitting sublayer density increases, the impact on voltage and electroluminescence peak (EL peak) is relatively small, while the external quantum efficiency (EQE) shows a slight improvement, and the lifetime improvement is very significant. This demonstrates that a higher light-emitting sublayer density is more beneficial to the luminescence performance of the blue phosphorescent material. The thickness of the complete display panel before and after heating is measured using an interferometer to determine the thickness expansion amplitude. A smaller thickness expansion amplitude indicates better film quality of the first light-emitting sublayer 1033. Devices with higher light-emitting layer density and better luminescence performance exhibit smaller thickness expansion amplitudes after heating. The smaller the thermal color shift, the more uniform the display, and the longer the lifespan of the display panel.

[0087] Please continue to refer to this. Figure 1 The charge generation layer 104 includes a first charge generation layer 1041 and a second charge generation layer 1042. The first charge generation layer 1041 is disposed on the side of the first light-emitting layer 103 away from the first electrode 102, and the second charge generation layer 1042 is disposed on the side of the first charge generation layer 1041 away from the first light-emitting layer 103.

[0088] In this embodiment, the first charge generation layer 1041 is an n-type charge generation layer, and the material of the first charge generation layer 1041 includes an n-type charge generation material. The second charge generation layer 1042 is a p-type charge generation layer, and the material of the second charge generation layer 1042 includes a p-type charge generation material. In this embodiment, due to the presence of the charge generation layer 104, a charge carrier injected by the electrode can flow sequentially through two independent light-emitting units, significantly improving the luminous efficiency.

[0089] The first light-emitting layer 103 further includes a first hole injection sublayer 1031, a first hole transport sublayer 1032, a first electron transport sublayer 1034, and a first electron injection sublayer 1035. The first hole injection sublayer 1031 and the first hole transport sublayer 1032 are sequentially disposed on the first electrode 102. The first light-emitting sublayer 1033 is disposed on the first hole transport sublayer 1032. The first electron transport sublayer 1034 and the first electron injection sublayer 1035 are sequentially disposed on the first light-emitting sublayer 1033. The first charge generation layer 1041 and the second charge generation layer 1042 are sequentially disposed on the first electron injection sublayer 1035. The second light-emitting layer 105 further includes a second hole injection sublayer 1051, a second hole transport sublayer 1052, a second electron transport sublayer 1054, and a second electron injection sublayer 1055. The second hole injection sublayer 1051 and the second hole transport sublayer 1052 are sequentially disposed on the second charge generation layer 1042. The second electron transport sublayer 1054 and the second electron injection sublayer 1055 are sequentially disposed on the side of the second light-emitting sublayer 1053 away from the second hole transport sublayer 1052.

[0090] Please refer to Figure 5 , Figure 5 This is a diagram illustrating an energy level arrangement of a display panel provided in an embodiment of this application. In some embodiments, the lowest empty orbital energy level and the highest occupied orbital energy level of the first hole transport sublayer 1032, the first light-emitting sublayer 1033, and the first electron transport sublayer 1034 decrease sequentially.

[0091] In this embodiment, since the lowest unoccupied orbital energy level and the highest occupied orbital energy level of the first hole transport sublayer 1032, the first light-emitting sublayer 1033 and the first electron transport sublayer 1034 decrease sequentially, that is, the highest occupied orbital energy level and the lowest unoccupied orbital energy level of each adjacent organic film layer material are arranged in a stepwise manner, such an arrangement is conducive to the balanced injection and transport of charge carriers, reduces the energy level barrier, thereby improving the luminous efficiency of the display panel 100, and thus obtaining the optimal device performance.

[0092] It should be noted that the highest occupied orbital refers to the molecular orbital with the highest energy among the electron-occupied molecular orbitals, also known as the highest occupied molecular orbital. Among the unoccupied molecular orbitals, the lowest energy molecular orbital is called the lowest vacant orbital.

[0093] In some embodiments, electrons and holes can be injected in a balanced 1:1 ratio to achieve efficient utilization of electrons and holes.

[0094] To lower the potential barrier for hole injection from the first electrode 102, enabling efficient hole injection into the display panel 100, the hole transport rate is generally greater than the electron transport rate. To ensure recombination of injected electrons and holes in the first light-emitting sublayer 1033, the energy level structures of the first hole transport sublayer 1032 and the first light-emitting sublayer 1033 are matched, and their hole migration speeds are also matched. To lower the potential barrier for electron injection from the second electrode 106, enabling efficient electron injection into the display panel 100, the material of the first electron injection sublayer 1035 is selected to ensure efficient electron injection into the display panel 100 from the second electrode 106. To lower the potential barrier for hole injection from the anode, enabling efficient hole injection into the OLED device, the matching of the material energy levels and the material of the second electrode 106 needs to be considered when selecting the electron injection layer material.

[0095] In some embodiments, the lowest empty orbital energy level and the highest occupied orbital energy level of the first hole injection sublayer 1031, the first hole transport sublayer 1032, the first light emission sublayer 1033, the first electron transport sublayer 1034, and the first electron injection sublayer 1035 decrease sequentially. This arrangement facilitates balanced carrier injection and transport, lowers the energy level barrier, and further improves the luminous efficiency of the display panel 100, thereby achieving optimal device performance.

[0096] In some embodiments, the energy level difference between the highest occupied orbitals of the first hole transport sublayer 1032 and the first light-emitting sublayer 1033 is less than or equal to 0.2 eV, and the energy level difference between the lowest empty orbitals of the first electron transport sublayer 1034 and the first light-emitting sublayer 1033 is less than or equal to 0.2 eV. This reduces the potential barrier between adjacent organic film layers and further improves the luminous efficiency of the display panel 100.

[0097] Specifically, the energy level difference between the highest occupied orbitals of the first hole transport sublayer 1032 and the first light-emitting sublayer 1033 can be any one of 0.05 eV, 0.08 eV, 0.12 eV, 0.15 eV, 0.18 eV, or 0.2 eV. Similarly, the energy level difference between the lowest empty orbitals of the first hole transport sublayer 1032 and the first light-emitting sublayer 1033 can be any one of 0.05 eV, 0.08 eV, 0.12 eV, 0.15 eV, 0.18 eV, or 0.2 eV. This reduces the potential barrier between adjacent organic film layers, further improving the luminous efficiency of the display panel 100.

[0098] In some embodiments, the lowest empty orbital energy level and the highest occupied orbital energy level of the second hole transport sublayer 1052, the second light-emitting sublayer 1053, and the second electron transport sublayer 1054 decrease sequentially.

[0099] In this embodiment, since the lowest unoccupied orbital energy level and the highest occupied orbital energy level of the second hole transport sublayer 1052, the second light-emitting sublayer 1053, and the second electron transport sublayer 1054 decrease sequentially, that is, the highest occupied orbital energy level and the lowest unoccupied orbital energy level of each adjacent organic film layer material are arranged in a stepped manner, such an arrangement is conducive to the balanced injection and transport of charge carriers, reduces the energy level barrier, thereby improving the luminous efficiency of the display panel 100, and thus obtaining the optimal device performance.

[0100] In some embodiments, electrons and holes can be injected in a balanced 1:1 ratio to achieve efficient utilization of electrons and holes.

[0101] To lower the potential barrier for hole injection from the first electrode 102, enabling efficient hole injection into the display panel 100, the hole transport rate is generally greater than the electron transport rate. To ensure recombination of injected electrons and holes in the first light-emitting sublayer 1033, the energy level structures of the second hole transport sublayer 1052 and the second light-emitting sublayer 1053 are matched, and their hole migration speeds are also matched. To lower the potential barrier for electron injection from the second electrode 106, enabling efficient electron injection into the display panel 100, the material of the second electron injection sublayer 1055 is selected to ensure efficient electron injection into the display panel 100 from the second electrode 106. To lower the potential barrier for hole injection from the anode, enabling efficient hole injection into the OLED device, the matching of the material energy levels and the material of the second electrode 106 needs to be considered when selecting the electron injection layer material.

[0102] In some embodiments, the lowest empty orbital energy level and the highest occupied orbital energy level of the second hole injection sublayer 1051, the second hole transport sublayer 1052, the second light emission sublayer 1053, the second electron transport sublayer 1054, and the second electron injection sublayer 1055 decrease sequentially. This arrangement facilitates balanced carrier injection and transport, lowers the energy level barrier, and further improves the luminous efficiency of the display panel 100, thereby achieving optimal device performance.

[0103] In some embodiments, the energy level difference between the highest occupied orbitals of the second hole transport sublayer 1052 and the second light-emitting sublayer 1053 is less than or equal to 0.2 eV, and the energy level difference between the lowest empty orbitals of the second electron transport sublayer 1054 and the second light-emitting sublayer 1053 is less than or equal to 0.2 eV. This reduces the potential barrier between adjacent organic film layers and further improves the luminous efficiency of the display panel 100.

[0104] Specifically, the energy level difference between the highest occupied orbitals of the second hole transport sublayer 1052 and the second light-emitting sublayer 1053 can be any one of 0.05 eV, 0.08 eV, 0.12 eV, 0.15 eV, 0.18 eV, or 0.2 eV. Similarly, the energy level difference between the lowest empty orbitals of the second hole transport sublayer 1052 and the second light-emitting sublayer 1053 can be any one of 0.05 eV, 0.08 eV, 0.12 eV, 0.15 eV, 0.18 eV, or 0.2 eV. This reduces the potential barrier between adjacent organic film layers, further improving the luminous efficiency of the display panel 100.

[0105] In some embodiments, the display panel 100 further includes a thin-film transistor structure layer disposed on the substrate 101, which is used to drive the display panel 100 to emit light.

[0106] In some embodiments, the first electrode 102 is the anode, and the material of the first electrode 102 is a laminate of indium tin oxide, silver, and indium tin oxide. The second electrode 106 is the cathode, and the material of the second electrode 106 is a magnesium and silver alloy.

[0107] Accordingly, this application also provides a method for manufacturing a display panel, the method for manufacturing the display panel 100 includes the following steps:

[0108] Step B001: Provide a substrate.

[0109] Step B002: Form a first electrode on the substrate, wherein the first electrode is a stacked material of indium tin oxide, silver and indium tin oxide.

[0110] Step B003: Form a first light-emitting layer on the first electrode. The first light-emitting layer comprises a first hole injection sublayer, a first hole transport sublayer, a first light-emitting sublayer, a first electron transport sublayer, and a first electron injection sublayer, stacked sequentially. The material of the first hole transport sublayer may be NPB (N,N′-di(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4-4′-diamine), with a thickness between 10 nm and 60 nm. In a specific embodiment, the thickness of the first hole transport sublayer may be 20 nm. The first light-emitting sublayer is an organic light-emitting material, and the concentration of the doped organic light-emitting material is less than 2%. The evaporation rate of the light-emitting sublayer is less than or equal to 1.5 Å / s. In one embodiment, the evaporation rate of the first light-emitting sublayer is 1.0 Å / s. The host material of the organic light-emitting material can be at least one of DCB, CBP, CDBP, CBPE, mCP, BCzph, CzC, 4CzPBP, TPBi, BCzTPM, BCPPA, NPB, TAPC, and Irpic. The thickness of the first light-emitting sublayer can be between 10 nanometers and 30 nanometers. In a specific embodiment, the thickness of the first light-emitting sublayer can be 20 nanometers.

[0111] In some embodiments, the step of forming a first light-emitting layer on the first electrode includes forming a first electron-blocking layer on a first hole transport layer. The material of the first electron-blocking layer may be TAPC (4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline]). The thickness of the first electron-blocking layer may be between 2 nanometers and 10 nanometers. In a specific embodiment, the thickness of the first electron-blocking layer may be 5 nanometers.

[0112] Step B004: A charge generation layer is formed on the first light-emitting layer. The charge generation layer includes a first charge generation layer and a second charge generation layer. The first charge generation layer is an n-type charge generation layer, and the second charge generation layer is a p-type charge generation layer.

[0113] In some embodiments, the first charge generation layer comprises an n-type charge generation material, such as TPBi doped with 5% Yb, with a thickness of 100 nm, and the second charge generation layer comprises a p-type charge generation material, such as NPB doped with 5% HATCN (2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzophenanthrene), with a thickness of 100 nm.

[0114] Step B004: Form a second light-emitting layer on the charge generation layer, wherein the second light-emitting layer comprises a second hole injection sublayer, a second hole transport sublayer, a second light-emitting sublayer, a second electron transport sublayer, and a second electron injection sublayer stacked sequentially. The material of the second hole transport sublayer may be NPB (N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4-4′-diamine), with a thickness between 10 nm and 60 nm. In a specific embodiment, the thickness of the second hole transport sublayer may be 20 nm. The second light-emitting sublayer is an organic light-emitting material, and the concentration of the doped organic light-emitting material is less than 2%. The evaporation rate of the light-emitting sublayer is less than or equal to 1.5 Å / s. In one embodiment, the evaporation rate of the second light-emitting sublayer is 1.0 Å / s. The host material of the organic light-emitting material can be at least one of DCB, CBP, CDBP, CBPE, mCP, BCzph, CzC, 4CzPBP, TPBi, BCzTPM, BCPPA, NPB, TAPC, and Firmic. The thickness of the second light-emitting sublayer can be between 10 nanometers and 30 nanometers. In a specific embodiment, the thickness of the second light-emitting sublayer can be 20 nanometers.

[0115] In some embodiments, the second hole transport sublayer is NPB with a thickness of 20 nm. The second electron transport sublayer is TPBi with a thickness of 35 nm. The second electron injection sublayer is Yb (ytterbium) with a thickness of 1 nm.

[0116] In some embodiments, the step of forming a second light-emitting layer on the charge-generating layer includes forming a second electron-blocking layer on the second hole-transporting layer. The material of the second electron-blocking layer may be TAPC (4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline]). The thickness of the second electron-blocking layer may be between 2 nanometers and 10 nanometers. In a specific embodiment, the thickness of the second electron-blocking layer may be 5 nanometers.

[0117] Step B005: Deposit a second electrode on the side of the second light-emitting layer that is away from the charge-generating layer. The material of the second electrode may include silver and magnesium. The deposition rate of the second electrode is less than or equal to 3 angstroms / second; in one embodiment, the deposition rate may be 2 angstroms / second. The thickness of the second electrode is between 10 nanometers and 50 nanometers; for example, the thickness of the second electrode may be 13.2 nanometers.

[0118] In some embodiments, the Mg doping concentration of the second electrode is 9%.

[0119] In summary, although the present application has disclosed the preferred embodiments as described above, the above preferred embodiments are not intended to limit the present application. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be determined by the scope defined in the claims.

Claims

1. A display panel, characterized in that, include: Substrate, A first electrode is disposed on the substrate; A light-emitting functional layer is disposed on the side of the first electrode away from the substrate. The light-emitting functional layer includes a first light-emitting layer, a charge-generating layer and a second light-emitting layer sequentially disposed on the first electrode. The first light-emitting layer includes a first light-emitting sublayer and the second light-emitting layer includes a second light-emitting sublayer. The second electrode is disposed on the side of the second light-emitting layer away from the charge-generating layer; The first light-emitting sublayer has a first film compactness parameter, which is calculated by the following formula: X1=ΔF1 / ΔH1, where ΔF1 is the difference between different forces in the thickness direction of the film, ΔH1 is the thickness difference of the stressed part of the film under different forces, and the first film compactness parameter is greater than or equal to -1.7N / cm and less than 0. The second light-emitting sublayer has a second thin film compactness parameter, which is calculated by the following formula: X2=ΔF2 / ΔH2, where ΔF2 is the difference of different forces in the thickness direction of the thin film, ΔH2 is the thickness difference of the stressed part of the thin film under different forces, and the second thin film compactness parameter is greater than or equal to -1.7N / cm and less than 0.

2. The display panel according to claim 1, characterized in that, The first and second film compactness parameters are determined by the thickness deformation of the stressed portion of the film under unit force in the thickness direction.

3. The display panel according to claim 1, characterized in that, When the display panel is powered on, the ratio between the dimensional deformation of the light-emitting functional layer and the original shape and size of the light-emitting functional layer is less than or equal to 7.5%.

4. The display panel according to claim 3, characterized in that, When the display panel is powered on, the ratio between the expansion of the thickness of the light-emitting functional layer and the original thickness of the light-emitting functional layer is less than or equal to 7.5%.

5. The display panel according to claim 1, characterized in that, When the display panel is heated, the ratio between the dimensional deformation of the light-emitting functional layer and the original shape and size of the light-emitting functional layer is less than or equal to 13%.

6. The display panel according to claim 5, characterized in that, When the display panel is heated, the ratio between the expansion of the thickness of the light-emitting functional layer and the original thickness of the light-emitting functional layer is less than or equal to 13%.

7. The display panel according to claim 1, characterized in that, The charge generation layer includes a first charge generation layer and a second charge generation layer. The first charge generation layer is disposed on the side of the first light-emitting layer away from the first electrode and includes an n-type charge generation material. The second charge generation layer is disposed on the side of the first charge generation layer away from the first light-emitting layer and includes a p-type charge generation material.

8. The display panel according to claim 7, characterized in that, The first light-emitting layer includes a first hole injection sublayer, a first hole transport sublayer, the first light-emitting sublayer, a first electron transport sublayer, and a first electron injection sublayer, which are stacked sequentially. The second light-emitting layer includes a second hole injection sublayer, a second hole transport sublayer, a second light-emitting sublayer, a second electron transport sublayer, and a second electron injection sublayer, which are stacked sequentially.

9. The display panel according to claim 1, characterized in that, The first luminescent sublayer comprises a blue phosphorescent material or a blue fluorescent material, and the second luminescent sublayer comprises a blue phosphorescent material or a blue fluorescent material.

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